Ice-shelf changes in Pine Island Bay, Antarctica, 1947-2000

Eric Rignot

doi:10.3189/172756502781831386

Abstract

AbstractAerial photographs from 1947 and 1966, satellite optical imagery from 1973 and 1980, and interferometric synthetic aperture radar (InSAR) data from 1992, 1996 and 2000 are employed to detect ice-shelf changes in Pine Island Bay, Antarctica. The front position of the fast-flowing central ice shelf did not migrate discernibly over the past 50 years. New cracks and rifts appeared in the 1990s, however, that reveal a major weakening of the ice shelf. At the grounding-line center, the ice shelf thinned 21 m in 8 years. The northern, slow-moving ice shelf also shows signs of decay: (1) its calving front is retreating at an accelerating rate; and (2) the ice shelf is slowly unpinning from its bedrock anchors. These changes are taking place in a region well beyond the temperature-dependent limit of viability of ice shelves, and hence differ from those observed along the Antarctica Peninsula. They are likely due to a change in oceanic forcing, not to a change in air temperature. One possibility is that the documented intrusion of warm circumpolar deep water on the continental shelf has increased basal melting compared to that required to maintain the ice shelf in a state of mass balance, and that this has triggered a general retreat of ice in this sector.

Highlights

Pine Island Bay is the least studied drainage system of West Antarctica (Vaughan and others, 2001) despite its likely importance to the stability of the West Antarctic ice sheet (Hughes, 1981)
Surface topography was derived from a combination of interferometric synthetic aperture radar (InSAR) data and radar altimetry data.The results show that the grounding-line retreat is most pronounced along Pine Island Glacier, which continued its retreat after 1996
An analysis of glacier imagery collected in Pine Island Bay over half a century suggests that its floating glacier ice is retreating and weakening, with a marked acceleration of that trend in the last decade

Summary

Introduction

Pine Island Bay is the least studied drainage system of West Antarctica (Vaughan and others, 2001) despite its likely importance to the stability of the West Antarctic ice sheet (Hughes, 1981). The data revealed that rapid changes are taking place in this sector: (1) the grounding line of Pine Island Glacier retreated 5 km between 1992 and 1996 at the glacier center and less on its sides (Rignot, 1998); (2) the drainage basin of Thwaites and Pine Island Glaciers thinned 10 cm a^1in the 1990s (Wingham and others, 1998); (3) Pine Island Glacier thinned 1.6 m a^1 in its lower reaches, with thinning concentrated in areas of fast flow (Shepherd and others, 2001); (4) the basin of Thwaites Glacier is significantly out of balance and its grounding line is retreating (Rignot, 2001); and (5) the flow of Pine Island Glacier accelerated 18% over the last 8 years over a region 4150 km in length, including the ice shelf, and the glacier thinned as a result of the acceleration (Rignot and others, 2002).

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Results

Discussion

Conclusion